27 research outputs found
Review on District Cooling and Its Application in Energy Systems
This chapter investigates the implementation of district cooling systems by exploring several research studies reported in the literature. The topics addressed include typologies and design parameters, benefits and limitations, applications of the system, and the technology readiness level. District cooling systems are generally regarded as cost-efficient and environmentally friendly solutions. One might think that district cooling is only a solution for areas with a very warm climate. However, based on the reported results of the surveyed studies, the number of operating district cooling systems has increased over the years, with the Scandinavian countries taking the lead in this market within European countries. Implementation of these systems concluded reduction in primary energy and electricity use, they also proved to be an environmentally efficient way
Viewpoints on Environmental Assessment of Building Certification Method - Miljöbyggnad
Production, management, use, and end-of-life of buildings has a large impact on climate change. Therefore, environmental targets are set to lower the greenhouse gas (GHG) emissions from the building sector. To reach these targets building regulation and voluntary environmental assessment methods (EAMs) that evaluate and certify the buildingâs environmental impact are put forward as tools to push the building sector towards lower GHG emissions. In Sweden, building design is governed by building regulations and the dominant EAM is âMiljöbyggnadâ (MB) (âEnvironmental buildingâ). Today, more than 1900 buildings have been certified by MB and it has influenced the building and property sector. In this chapter the potential impact MB and the linked Swedish building regulations have on building performance, energy use and GHG emissions, will be reviewed and discussed. The analysis investigates several of the MBâs indicators, evaluate to what degree EAMs can influence the design of the building and the energy system to lower the energy use and GHG emissions based on material choices. The analysis presents important aspects that may influence the design of the building and its energy system and what challenges and possibilities the indicators, criteria and regulations can have on buildings and climate change. In addition, some modification and suggestion for improvements are presented
Resilient cooling strategies â A critical review and qualitative assessment
The global effects of climate change will increase the frequency and intensity of extreme events such as heatwaves and power outages, which have consequences for buildings and their cooling systems. Buildings and their cooling systems should be designed and operated to be resilient under such events to protect occupants from potentially dangerous indoor thermal conditions. This study performed a critical review on the state-of-the-art of cooling strategies, with special attention to their performance under heatwaves and power outages. We proposed a definition of resilient cooling and described four criteria for resilienceâabsorptive capacity, adaptive capacity, restorative capacity, and recovery speed âand used them to qualitatively evaluate the resilience of each strategy. The literature review and qualitative analyses show that to attain resilient cooling, the four resilience criteria should be considered in the design phase of a building or during the planning of retrofits. The building and relevant cooling system characteristics should be considered simultaneously to withstand extreme events. A combination of strategies with different resilience capacities, such as a passive envelope strategy coupled with a low-energy space-cooling solution, may be needed to obtain resilient cooling. Finally, a further direction for a quantitative assessment approach has been pointed out
Natural Ventilation and Air Infiltration in Large SingleâZone Buildings : Measurements and Modelling with Reference to Historical Churches
Natural ventilation is the dominating ventilation process in ancient buildings like churches, and also in most domestic buildings in Sweden and in the rest of the world. These buildings are naturally ventilated via air infiltration and airing. Air infiltration is the airflow through adventitious leakages in the building envelope, while airing is the intentional air exchange through large openings like windows and doors. Airing can in turn be performed either as single-sided (one opening) or as cross flow ventilation (two or more openings located on different walls). The total air exchange affects heating energy and indoor air quality. In churches, deposition of airborne particles causes gradual soiling of indoor surfaces, including paintings and other pieces of art. Significant amounts of particles are emitted from visitors and from candles, incense, etc. Temporary airing is likely to reduce this problem, and it can also be used to adjust the indoor temperature. The present study investigates mechanisms and prediction models regarding air infiltration and open-door airing by means of field measurements, experiments in wind tunnel and computer modelling. In natural ventilation, both air infiltration and airing share the same driving forces, i.e. wind and buoyancy (indoor-outdoor temperature differences). Both forces turn out to be difficult to predict, especially wind induced flows and the combination of buoyancy and wind. In the first part of the present study, two of the most established models for predicting air infiltration rate in buildings were evaluated against measurements in three historical stone churches in Sweden. A correction factor of 0.8 is introduced to adjust one of the studied models (which yielded better predictions) for fitting the large single zones like churches. Based on field investigation and IR-thermography inspections, a detailed numerical model was developed for prediction of air infiltration, where input data included assessed level of the neutral pressure level (NPL). The model functionality was validated against measurements in one of the case studies, indicating reasonable prediction capability. It is suggested that this model is further developed by including a more systematic calibration system for more building types and with different weather conditions. Regarding airing, both single-sided and cross flow rates through the porches of various church buildings were measured with tracer gas method, as well as through direct measurements of the air velocity in a porch opening. Measurement results were compared with predictions attained from four previously developed models for singleâsided ventilation. Models that include terms for wind turbulence were found to yield somewhat better predictions. According to the performed measurements, the magnitude of one hour single-sided open-door airing in a church typically yields around 50% air exchange, indicating that this is a workable ventilation method, also for such large building volumes. A practical kind of diagram to facilitate estimation of suitable airing period is presented. The ability of the IDA Indoor Climate and Energy (IDA-ICE) computer program to predict airing rates was examined by comparing with field measurements in a church. The programsâ predictions of single-sided airflows through an open door of the church were of the same magnitude as the measured ones; however, the effect of wind direction was not well captured by the program, indicating a development potential. Finally, wind driven air flows through porch type openings of a church model were studied in a wind tunnel, where the airing rates were measured by tracer gas. At single-sided airing, a higher flow rate was observed at higher wind turbulence and when the opening was on the windward side of the building, in agreement with field measurements. Further, the airing rate was on the order of 15 times higher at cross flow than at single-sided airing. Realization of cross flow thus seems highly recommendable for enhanced airing. Calibration constants for a simple equation for wind driven flow through porches are presented. The measurements also indicate that advection through turbulence is a more important airing mechanism than pumping.  The present work adds knowledge particularly to the issues of air infiltration and airing through doors, in large single zones. The results can be applicable also to other kinds of large single-zone buildings, like industry halls, atriums and sports halls.Naturlig ventilation Ă€r den dominerande ventilationsprocessen i Ă€ldre byggnader sĂ„som kyrkor, och Ă€ven i de flesta smĂ„hus i Sverige och övriga delar av vĂ€rlden. Luftinfiltration och vĂ€dring utgör viktiga komponenter i naturlig ventilation, dĂ€r luftinfiltration Ă€r luftflöde genom oavsiktliga lĂ€ckage i byggnadsskalet, medan vĂ€dring Ă€r avsiktligt luftutbyte genom stora öppningar sĂ„som fönster och dörrar/portar. VĂ€dring kan i sin tur ske ensidigt (genom en öppning) eller som tvĂ€rdrag (genom tvĂ„ eller flera öppningar belĂ€gna pĂ„ olika yttervĂ€ggar). Det totala luftutbytet pĂ„verkar vĂ€rmeförluster och inomhusluftens kvalitĂ©. I kyrkor orsakar avsĂ€ttning av luftpartiklar en gradvis nedsmutsning av invĂ€ndiga ytor, inklusive vĂ€ggmĂ„lningar och andra konstföremĂ„l. Betydande mĂ€ngder partiklar avges frĂ„n besökare, tĂ€nda ljus, rökelse, o.d. TillfĂ€llig vĂ€dring kan minska detta problem, men Ă€ven anvĂ€ndas för att justera innetemperaturen. Föreliggande studie analyserar mekanismer och predikteringsmodeller gĂ€llande luftinfiltration och dörrvĂ€dring genom fĂ€ltmĂ€tningar, vindtunnelförsök och datorsimuleringar. Luftinfiltration och vĂ€dring har samma drivkrafter, d.v.s. vind och termik (inneâute temperaturskillnader). BĂ„da dessa drivkrafter Ă€r svĂ„ra att predicera, sĂ€rskilt vindinducerade flöden och kombinationen av termik och vind. TvĂ„ av de mest etablerade modellerna för luftinfiltrationsprediktering i byggnader har utvĂ€rderats via mĂ€tningar i tre kulturhistoriska stenkyrkor i Sverige. En korrigeringsfaktor av 0,8 föreslĂ„s för bĂ€ttre prediktion av den ena modellen (som gav bĂ€st resultat) gĂ€llande höga en-zonsbyggnader sĂ„som kyrkor. En detaljerad numerisk modell Ă€r utvecklad för luftinfiltrationsprediktering, dĂ€r indata baseras pĂ„ fĂ€ltundersökningar, inkl. IR-termografering och uppmĂ€tt av neutrala tryckplanet (NPL). Modellens funktionalitet har validerats via mĂ€tningar i en av fallstudierna och pekar pĂ„ tĂ€mligen god prediktionsprestanda. Vidare utveckling av modellen föreslĂ„s, inkl. ett mer systematiskt kalibreringssystem, för olika typer av byggnader och vĂ€derförhĂ„llanden. GĂ€llande vĂ€dring mĂ€ttes bĂ„de ensidigt flöde och tvĂ€rdrag genom portar i olika kyrkobyggnader med hjĂ€lp av spĂ„rgas samt direkta lufthastighetsmĂ€tningar i portöppning. MĂ€tresultaten jĂ€mfördes med erhĂ„llna prediktioner frĂ„n fyra tidigare utvecklade modeller för ensidig ventilation. De modeller som tog hĂ€nsyn till vindturbulens gav nĂ„got bĂ€ttre resultat. Enligt utförda mĂ€tningar medför en timmes ensidig portvĂ€dring i en kyrka cirka 50 % luftutbyte, vilket indikerar att detta Ă€r en tillĂ€mpbar ventilationsmetod, Ă€ven för sĂ„ pass stora byggnadsvolymer. Ett sĂ€rskilt vĂ€dringsdiagram presenteras, som syftar till att underlĂ€tta uppskattning av erforderlig vĂ€dringsperiod. Vidare studerades predikteringsprestanda hos IDA Indoor Climate and Energy (IDA-ICE) simuleringsprogram avseende vĂ€dring, dĂ€r simuleringsdata jĂ€mfördes med fĂ€ltmĂ€tningar i en kyrka. Programmets prediktion av ensidigt luftflöde genom en öppen kyrkport var av samma storlekordning som det uppmĂ€ta; dock klarade programmet inte av att hantera inverkan av vindriktning sĂ„ vĂ€l, vilket pekar pĂ„ en utvecklingspotential. Avslutningsvis undersöktes vinddrivet flöde igenom portöppningar i en kyrkmodell i vindtunnel, dĂ€r luftomsĂ€ttningen mĂ€ttes med hjĂ€lp av spĂ„rgasmetoden. Vid ensidig vĂ€dring observerades högre flöde vid högre vindturbulens och nĂ€r öppningen var pĂ„ vindsidan av byggnaden, i överensstĂ€mmelse med fĂ€ltmĂ€tningarna. Dessutom var vĂ€dringsflödet vid tvĂ€rdrag i storleksordningen 15 högre Ă€n det vid ensidig vĂ€dring. Det verkar alltsĂ„ som att man kan öka vĂ€dringstakten avsevĂ€rt om man kan Ă„stadkomma tvĂ€rdrag. Kalibreringskonstanter presenteras ocksĂ„ för en enkel ekvation för vinddrivet flöde genom portar. Vindtunnelstudien indikerar vidare att advektion genom turbulens Ă€r en viktigare vĂ€dringsmekanism Ă€n pumpning. Föreliggande arbete bidrar med kunskap speciellt kring luftinfiltration och vĂ€dring genom portar i höga en-zonsbyggnader. Resultaten kan Ă€ven vara tillĂ€mpliga pĂ„ andra typer av höga en-zonsbyggnader sĂ„som industrihallar, atrier/ljusgĂ„rdar och idrottshallar.Church projec
A case study of mapping the heating storage capacity in a multifamily building within a district heating network in mid-Sweden
The building sector accounts for a third of the total energy use in Sweden, and district heating provides half of the heating needs. The peak demand loads within a district heating network occur both regularly and irregularly and impose a burden on the energy company to fulfill the demand, often by using more expensive and less environmentally friendly resources (e.g., fossil fuels) instead of the waste heat from industry or biofuels. Heat storage during hours of less demand and prior to colder periods can be used for load management and sustainable planning of energy supply, as well as reduction of total greenhouse gas emissions. Thus, heat supply to the building can be lowered temporarily during the peak power period to utilize the stored thermal energy within the building thermal inertia. The use of indoor temperature decay and the delivery of heating power to a multifamily building are studied here, and heating storage capacity and thermal inertia are calculated. During the performed decay test, the energy supply was estimated to be reduced by 61% for 5 h, which resulted in only a 0.3 °C temperature decay. Therefore, the suggested method can shave eventual peaks in supplied heat with minimal influence on the thermal comfort
Development of a Numerical Air Infiltration Model Based On Pressurization Test Applied On a Church
Pressurization (blower door) test is a well-established standardized method, performed in order to quantify the total leakage in a building envelope. However, blower door results are not adequate to use when air leakage through the building envelope during natural conditions (non-pressurized) is to be estimated. A common assumption made when estimating air leakage during natural conditions, is that air leakage paths are evenly distributed in the areas of the building envelope. This assumption gives quite poor calculation results since different leakage configurations are often situated unevenly in the envelope. In order to improve the correspondence between Blower door and air leakage model results, more information on the types and locations of the leakage paths are required as input to simulation models. This paper investigates if additional information from visual inspection and IR-thermography observations at site can increase the precision when simulating air change rates due to air leakage in natural conditions. A numerical model is developed in this study by allocating leakage in various parts of the building envelope. The leakage allocation is based on visual inspection and IR-thermography observations at the site during the blower door test. This procedure is tested in the case study of a large single zone church. Blower door, neutral pressure level measurement and leakage allocation results are used as input in the numerical model. Model results are compared with tracer gas measurements and result accuracy is compared with results from the Lawrence Berkeley Laboratory model (LBL) and the Alberta Air Infiltration Model (AIM-2) for the same church. Church projec
Optimization of window-to-wall ratio for buildings located in different climates: an IDA-Indoor Climate and Energy simulation study
This study investigates different cases to obtain optimal Window-to-Wall ratio (WWR) in seven different climate conditions based on the KöppenâGeiger climate classification. The optimal WWR was decided based on the minimum amount of total energy use (total of cooling, heating, and lighting energy use) of a building model during a complete year. The impact of overhang and automatic blinds were assessed on the optimization of WWR for a building with integrated automatic lighting control. Moreover, three different windows with different U-values and features were employed in order to analyze their effect on the energy use and WWR of the building. IDA-Indoor Climate and Energy (IDA-ICE) was used to carry out the simulations. The software has been validated based on ASHRAE Standard 140. Based on each climate condition, orientation, employed window type, and comfort conditions, an optimal range with a specific combination of window with blind, overhang, or neither was found
Simulation of Ventilation Rates and Heat Losses during Airing in Large Single Zone Buildings in Cold Climates
Airing can be a solution to introduce extra ventilation in large single zone buildings, especially where there are large aggregations of people such as churches or atriums. In naturally ventilated domestic and ancient buildings, opening of a window or door can introduce extra fresh air and remove particles and other contaminants emitted from people and other sources such as lit candles in churches. However, the energy use might be an issue in cold climates, where airing might lead to waste of heated air, at the same time as indoor air temperatures can be uncomfortably low. In the present study, the energy loss and ventilation rate due to airing in a large single zone (church) building is investigated via IDA-ICE simulation on annual basis in cold weather conditions. The results can be used in order to prepare airing guidelines for large single zone buildings such as atriums, churches, industry halls and large sport halls. According to the results, one-hour of airing in the studied church building resulted in 40-50 % of exchanged room air and, if practiced once a week, an increase of around 1 % in heating energy.Forthcomming March 2019</p
A Study on Airing Through the Porches of a Historical Church â Measurements and IDA-ICE Modelling
In churches, intentional airing may be a measure to evacuate temporarily high levels of contaminants that are emitted during services and other occasions. Crucial contaminants include moisture and other emissions that may deteriorate and/or soil painted surfaces and other precious artefacts. Most old churches do not have any mechanical ventilation system or any purpose provided openings for natural ventilation, but the ventilation is governed by air infiltration. Enhanced airing may be achieved by opening external windows or doors. Thus, models provided in energy simulation programs should predict this kind of air flows correctly, also in order to get a proper estimation of the total energy use. IDA-ICE is examined here and the model for air flow through a large vertical opening used in the program is investigated. In the present study, field measurements were performed for airing rate in a historical church. In comparison with measured air flow rates, the simulated results were of the same magnitude, but the effect of wind direction was less considered by the simulation program.Church projec